Method for detecting the fuel level in the tank of a motor vehicle

Abstract

The level indicated on the instrument panel of the motor vehicle results from a processing operation, including the calculation of a weighted average value, whereby the effects of accidental phenomena such as agitation of the fuel within the tank during movement of the motor vehicle are dispensed with.

I claim: 
     
       1. A method for detecting and displaying outside the fuel level in the tank of a motor vehicle by means of apparatus which can output a signal indicative of the fuel level in the tank of the motor vehicle, comprising the steps of: memorizing for outside display a given value indicative of the fuel level in the tank of the motor vehicle, and   updating, at predetermined instants, said given value by detecting at least one newly measured value corresponding to said signal indicative of the fuel level in the tank of the motor vehicle output by said apparatus, calculating a weighted average value of said memorized value and said at least one newly measured value and memorizing said weight average value as an updated given value for outside display;   said updating of said given value being carried out at instants where said weighted average value is lower tha the given value previously memorized by a given amount while the ignition is in the "on" position and said updating of said given value being carried out to display a new value when the ignition is turned to the "on" position to reflect refilling of said tank a predetermined amount when the ignition was previously in the "off" position.   
     
     
       2. A method according to claim 1 wherein said weighted average valve is calculated as: ##EQU2## where v m  ' is said weighted average value, v m  is said given value, n n1  is said newly measured value and a and b are a first and second weighing constants respectively. 
     
     
       3. A method according to claim 2, wherein said second weighing constant (b) is selected substantially equal to two. 
     
     
       4. A method according to claim 2 wherein said first weighing constant (a) is selected substantially equal to 118. 
     
     
       5. A method according to claim 1, including the steps of detecting fuel consumption of a motor vehicle engine and updating said given value at predetermined instants corresponding to the consumption of a predetermined quantity of fuel by the engine. 
     
     
       6. A method according to claim 1, including the steps of detecting a number of rotations effected by a motor vehicle engine, and updating said given value at predetermined instants corresponding to the completion of a predetermined number of rotations by the engine. 
     
     
       7. A method according to claim 6, including the steps of: detecting rate of rotation of said motor vehicle engine   comparing the rate of rotation of the engine with a respective threshold level and generating a comparison signal having first and second different logic levels in dependence on the result of the comparison, and   updating said given value at predetermined instants corresponding to the completion by the engine of a first and second predetermined number of rotations when the comparison signal assumes the first and second logic levels, respectively.   
     
     
       8. A method according to claim 6, including the steps of detecting the actuation of a vehicle brake, and interrupting the detection of the number of rotations effected by the engine during actuation of the brake. 
     
     
       9. A method according to claim 6 wherein: said predetermined instants for updating said given value are identified by counting the completion, by the motor vehicle engine, of one of a first and a second number, lower than said first number, of engine rotations,   when said given value is updated, counting proceeds towards completion of said first number of engine rotations, and   when said given value is not updated, counting proceeds towards completion of said second number of engine rotations.   
     
     
       10. A method according to claim 9, wherein said first number is substantially equal to 18,000. 
     
     
       11. A method according to claim 10, wherein said second number is substantially equal to 5,000. 
     
     
       12. A method according to claim 1, wherein said given value is memorized for outside display as discrete units of counting, and where said weighted average is lower than the given value previously memorized of a given amount, the said new given value memorized is corrected to a value corresponding to a decrement of only one of the counting units relative to the given value previously memorized. 
     
     
       13. A method according to claim 1, including the steps of: keeping, upon stoppage of the motor vehicle engine, a record of said given value,   detecting, upon starting of the engine, a newly measured value provided by said apparatus,   comparing said given value of record which was kept upon stoppage of the engine with said newly measured value detected upon restarting of the engine, and   replacing said given value of record which was kept upon stoppage of the engine by said newly measured value detected on restarting of the engine only when said newly measured value detected on restarting of the engine is greater than the value of record which was kept upon stoppage of the engine by a predetermined amount.